Asymmetric wetting film-induced micro-jet deflection driven by transverse capillary imbalance

Oblique jetting induced by non-ideal wetting on the nozzle plate remains a critical and unpredictable challenge in high-precision inkjet printing. However, the exact transient mechanisms linking an asymmetric micro-liquid film to droplet deflection are still not fully understood. By combining three-dimensional multi-relaxation-time lattice Boltzmann method with high-speed microscopic experiments, this work systematically reveals the physical mechanism of micro-jet deflection induced by asymmetric liquid films. The asymmetric film creates a curvature difference across the gas–liquid interface, generating a transverse Laplace pressure difference that serves as the fundamental driving force for jet deflection. Based on the Young–Laplace equation, this work derived a scaling law coupling the degree of asymmetry (α), contact angle (θ), and Weber number (We), elucidating the competition between interfacial geometry and axial inertia. Parametric scans demonstrate that within the linear response regime, the tangent of the deflection angle exhibits a highly linear correlation with the comprehensive dimensionless parameter αF(θ)/We, achieving a linear coefficient of determination R2>0.98. Additionally, both experiments and simulations captured a trajectory bifurcation phenomenon during the droplet nonlinear breakup stage. The established scaling law and numerical model provide a predictive theoretical basis for precise micro-jet control and optimization of printhead manufacturing tolerances under complex wetting conditions.